Hot, Polluted Days Can Double Heart Attack Risk

By Dennis Thompson Health Day Reporter

TUESDAY, July 25, 2023 (HealthDay News) — The extreme heat and choking smoke from wildfires blanketing large swathes of the United States this summer are actively dangerous to heart health, a new study reports.

Days when searing heat combines with fine particulate air pollution can double the risk of a fatal heart attack, researchers have found.

“Exposure to heat waves interacts synergistically with fine particulate pollution to trigger more heart attack deaths,” said a lead researcher. Yuewei Liuassociate professor of epidemiology at Sun Yat-sen University School of Public Health in Guangzhou, China.

These results show the direct danger to human health posed by climate change, said Dr. Sanjay RajagopalanChief of Cardiovascular Medicine at University Hospitals Harrington Heart and Vascular Institute in Cleveland.

“The interaction of these two factors – wildfire smoke and high temperatures – when these two things happen together, further increases the risk of heart attack,” said Rajagopalan, who was not involved in the study. “With climate change, this is becoming a daily reality.”

For the new study, researchers analyzed more than 202,000 heart attack deaths that occurred between 2015 and 2020 in China’s Jiangsu province.

They also collected local measures of heat index and air pollution for the day and day before each heart attack, to assess the increased risk posed by the combination of heat and smog. The heat index takes into account both temperature and humidity.

It’s no news that air pollution increases the risk of heart attack, Rajagopalan said.

“The association between air pollution and heart attacks has been demonstrated time and time again,” he said. “This is a well-known risk.”

The fine particles are less than 2.5 microns in size, about 30 times smaller than the diameter of an average human hair, according to the US Environmental Protection Agency.

When inhaled deep into the lungs, this particulate pollution can irritate the lungs and blood vessels around the heart, the researchers said in briefing notes.

But researchers have only recently begun to understand how heat could harm heart health and how it could combine with air pollution to further increase risk, Rajagopalan said.

“The links between how temperature and air pollution can interact to amplify the risk to individuals become much clearer,” he said.

Liu and his colleagues found that heat alone is a danger to the heart:

But that was fair considering the extreme heat.

The risk of dying from a heart attack actually doubled on days of extreme heat and poor air quality. These days presented the greatest increase in risk of all the weather conditions studied.

The researchers also looked at the risk posed by cold snaps.

While extreme cold could increase the risk of death from heart attack by 4% to 12%, it did not combine with air pollution to significantly further amplify the risk, they found.

Previous studies have shown that high heat or air pollution can increase inflammation and stress in the body, Liu said.

What’s more, high temperatures can actually increase a person’s absorption of air pollutants, increasing blood flow and altering breathing patterns, he said.

Women were more likely than men to have a fatal heart attack on extreme heat days, and people aged 80 and over were at higher risk than young adults, according to the results.

However, everyone is at some level of risk when high heat and air pollution combine. The interactive effects of oppressive heat and smog did not vary by sex, age or economic status, the researchers concluded.

Rajagopalan said people should start paying frequent attention to air pollution levels reported on weather sites. On days when the air quality drops, they should stay indoors and use either an HVAC system with good filters or a portable air purifier to keep the air fresh.

Those who must venture outside should use an N95 filter mask to protect against airborne particles, he added.

People can also combat the heat by using fans and air conditioners, dressing appropriately, staying hydrated and installing blinds to reduce indoor temperatures, Liu said.

Rajagopalan said certain groups should be especially cautious: people with diabetes, children with respiratory conditions, people with COPD, organ transplant recipients, people with chronic kidney disease and survivors of previous heart attacks or strokes.

“These are the people who need to be really concerned and take protective measures,” he said.

The study was published July 24 in the journal Traffic.

SOURCES: Yuewei Liu, PhD, associate professor, epidemiology, Sun Yat-sen University School of Public Health, Guangzhou, China; Sanjay Rajagopalan, MD, chief, cardiovascular medicine, University Hospitals Harrington Heart and Vascular Institute, Cleveland; TrafficJuly 25, 2023

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